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Four Strands of Science Learning

By looking much more deeply at how students learn science, recent research has produced new ways of thinking about what happens in science classrooms.

Books on science education have often drawn a fairly sharp distinction between scientific content and scientific processes. Content has been seen as the accumulated results of science—the observations, facts, and theories that students are expected to learn. Processes have been seen as the scientific skills that students are expected to master—skills like designing an experiment, making measurements, or reporting results.

Underlying the arguments in this book, however, is a new way of thinking about what it means to be proficient in science and a new framework for moving toward and achieving proficiency. This framework rests on a view of science as both a body of knowledge and an evidence-based, model-building enterprise that continually extends, refines, and revises knowledge. This framework moves beyond a focus on the dichotomy between content or knowledge and process skills, recognizing instead that, in science, content and process are inextricably linked.

This link between content and process is vital because scientific processes almost always take place when students are considering specific scientific content. When children use their ideas about the natural world to design investigations or argue about evidence, it strengthens their understanding of both the phenomena and the means used to investigate those phenomena. Moreover, separating content and process is inconsistent with what is now known about the way scientists actually do science.

Instead of drawing a distinction between content and process, we’ll define and describe four learning “strands” that encompass the knowledge and reasoning skills that students eventually must acquire to be considered proficient in science.



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These learning strands also incorporate the scientific practices that students need to master in order to demonstrate their proficiency. The strands of proficiency build on the helpful contributions of science stan- dards documents such as the Benchmarks for Science Literacy and the National Science Education Standards. These documents set out to characterize the concep- tual goals of science education and call for greater emphasis on science as inquiry. The strands of proficiency provide a framework for thinking about elements of scientific knowledge and practice. They can be useful to educators in their effort to plan and assess student learning in classrooms and across school systems. They can also be a helpful tool for identifying the science that is emphasized in a given curriculum guide, textbook, or assessment. The Four Strands The strands offer a new perspective on what is learned during the study of science, and they embody the idea of knowledge in use—the idea that students’ knowledge is not static. Instead, students bring certain capabilities to school and then build on those capabilities throughout their K-12 science education experiences, both inside and outside the classroom. Proficiency involves using all four strands to engage successfully in scientific practices. Another important aspect of the strands is that they are intertwined, much like the strands of a rope.1 Research suggests that each strand supports the oth- ers, so that progress along one strand promotes progress in the others. For exam- ple, there is evidence that students can make substantial gains in their conceptual knowledge of science when given opportunities to “do” science, and scientific rea- soning tends to be strongest in domains in which a person is more knowledgeable. Students are more likely to make progress in science when classrooms provide opportunities to advance across all four strands. Many science educators may want to interpret the strands in light of the cur- rent language and concepts of science education—for example, mapping the strands to the content, process, and nature of science, and participation, respectively. But it is important to note that the strands were developed because the Committee on Science Learning thought current assumptions about what constitutes the “content, process, and nature of science” are inadequate. In a sense, the first three strands revise and expand common ideas about the content, process, and nature of science to better reflect research and to include greater emphasis on the application of ideas. 18 Ready, Set, SCIENCE!

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Strand 1: Understanding Scientific Explanations To be proficient in science, students need to know, use, and interpret scientific explanations of the natural world. They must understand interrelations among central scientific concepts and use them to build and critique scientific arguments. This strand includes the things that are usually categorized as content, but it focuses on concepts and the links between them rather than on discrete facts. It also includes the ability to use this knowledge. For example, rather than memorizing a definition of natural selection, a child who demonstrates proficiency with scientific explanations would be able to apply the concept in novel scenarios. Upon first encountering a species, the child could hypothesize about how naturally occurring variation led to the organism’s suitability to its environment. Part of this strand involves learning the facts, concepts, principles, laws, theories, and models of science. As the National Science Education Standards state: “Understanding science requires that an individual integrate a complex structure of many types of knowledge, including the ideas of science, rela- tionship between ideas, reasons for these relationships, ways to use the ideas to explain and predict other natural phenomena, and ways to apply them to many events.”2 Strand 2: Generating Scientific Evidence Evidence is at the heart of scientific practice. Proficiency in science entails gener- ating and evaluating evidence as part of building and refining models and expla- nations of the natural world. This strand includes things that might typically be thought of as “process,” but it shifts the notion to emphasize the theory and model-building aspects of science. Strand 2 encompasses the knowledge and skills needed to build and refine models and explanations, design and analyze investigations, and construct and defend arguments with evidence. For example, this strand includes recognizing when there is insufficient evidence to draw a conclusion and determining what kind of additional data are needed. This strand also involves mastering the conceptual, mathematical, physical, and computational tools that need to be applied in constructing and evaluating knowledge claims. Thus, it includes a wide range of practices involved in design- ing and carrying out a scientific investigation. These include asking questions, deciding what to measure, developing measures, collecting data from the measures, 19 Four Strands of Science Learning

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structuring the data, interpreting and evaluating the data, and using results to develop and refine arguments, models, and theories. Strand 3: Reflecting on Scientific Knowledge Scientific knowledge builds on itself over time. Proficient science learners understand that scientific knowledge can be revised as new evidence emerges. They can also track and reflect on their own ideas as those ideas change over time. This strand includes ideas usually considered part of understanding the “nature of science,” such as the history of scientific ideas. However, it focuses more on how scientific knowledge is constructed. That is, how evidence and arguments based on that evidence are generated. It also includes students’ abil- ity to reflect on the status of their own knowledge. Four Strands of Science Learning Strand 3 brings the nature of science into Strand 1: Understanding Scientific Explanations practice, encouraging stu- Strand 2: Generating Scientific Evidence dents to learn what it feels Strand 3: Reflecting on Scientific Knowledge like to do science as well as to understand what Strand 4: Participating Productively in Science the game of science is all about. Strand 3 focuses on students’ understanding of science as a way of knowing. Scientific knowl- edge is a particular kind of knowledge with its own sources, justifications, and uncertainties. Students recognize that predictions or explanations can be revised on the basis of seeing new evidence, learning new facts, or developing a new model. In this way, students learn that they can subject their own knowl- edge to analysis. When students understand the nature and development of scientific knowl- edge, they know that science entails searching for core explanations and the con- nections between them. Students recognize that there may be multiple interpreta- tions of the same phenomenon. They understand that explanations are increasing- ly valuable as they account for the available evidence more completely. They also recognize the value of explanations in generating new and productive questions for research. 20 Ready, Set, SCIENCE!

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Strand 4: Participating Productively in Science Science is a social enterprise governed by a core set of values and norms for par- ticipation. Proficiency in science entails skillful participation in a scientific com- munity in the classroom and mastery of productive ways of representing ideas, using scientific tools, and interacting with peers about science. This strand calls for students to understand the appropriate norms for presenting scientific argu- ments and evidence and to practice productive social interactions with peers in the context of classroom science investigations. It also includes the motivation and attitudes that provide a foundation for students to be actively and productively involved in science classrooms. Strand 4 puts science in motion and in social con- text, emphasizing the importance of doing science and doing it together in groups. Like scientists, science students benefit from sharing ideas with peers, building interpretive accounts of data, and working together to discern which accounts are most persuasive. Strand 4 is often completely overlooked by educators, yet research indicates that it is a critical component of science learning, particularly for students from populations that are underrepresented in science. Students who see science as valu- able and interesting tend to be good learners and participants in science. They believe that steady effort in understanding science pays off—not that some people understand science and other people never will. The best way to begin thinking about the four strands of scientific profi- ciency and their interconnections is to see them at work in a classroom, as demon- strated in the following case study. 21 Four Strands of Science Learning

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Science Class BIODIVERSITY IN A CITY SCHOOLYARD3 Gregory Walker taught fifth grade in a predomi- were asked to do the best they could to meet the nantly low-income urban school in northwestern state’s science standards and prepare the students Massachusetts. It was his fourth year teaching, and for the fifth-grade state test in science. he was still learning how to manage a classroom Mr. Walker’s science class used an out-of-date and how to plan and orchestrate rigorous learning textbook and several old science kits that were miss- activities with an extremely heterogeneous group ing some key materials. He often stayed up late of students. His school district was working hard to at night trying to come up with interesting science raise student achievement to meet the demands of activities, but he never felt he knew enough to the state tests. Over 75 percent of the students in his “invent” great science lessons. He was, however, school were eligible for free or reduced-price lunches, very interested in teaching biodiversity, a topic emphasized in the national and state standards, even though the topic was not well developed in either his textbook or the available kits. Mr. Walker’s interest in biodiversity was not without foundation. He had taken a field biology course in college taught by a charismatic profes- sor. She explained to her students that biodiversity demanded mastery of a world of details, while phys- ics, chemistry, and the mechanistic aspects of biology more often required comprehension of core princi- ples and the skills needed to apply them. The ability to teach biodiversity, she said, entailed knowledge of the characteristics and behaviors that distinguish and his district was considered an “underperforming” individuals, species, genera, families, orders, and district and was under close scrutiny by the state. classes from each other. It required helping students Despite these challenges, the teachers at Mr. acquire both the tools and propensities to see and Walker’s school were collegial, energetic, willing characterize variation within and between species. It to open their doors to colleagues and parents, and required a comprehensive knowledge of ecosystem eager to share their successes with one another. For types and functions. And it required an awareness the past several years, the school had worked hard on of evolutionary, geological, and human history. improving literacy and mathematics achievement with For these reasons, her class, even though it solid results. Now the school was turning its atten- was offered through the biology department, was tion to science. designed to teach students how to teach biodiver- The school district had appointed a committee of sity. She hoped that they, in turn, would teach biodi- teachers and curriculum specialists to work together versity to others. for a year to come up with a recommendation for a Mr. Walker decided that he could apply many of new science curriculum. In the meantime, teachers the lessons he had learned during his college class 22 Ready, Set, SCIENCE!

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to the fifth-grade science class he would be teaching distributions of selected attributes in populations, that year. Because a major part of his college course giving concrete meaning to differences in levels on biodiversity had been preparing a local field guide of analysis. based on weekend trips to a field station, he and a Moreover, in preparation, Mr. Walker and Ms. colleague, second-grade teacher Alicia Rivera, decided Rivera spent time discussing the science behind their to work together to develop a yearlong project map- schoolyard investigation. They sought out field ping the plants and animals in their schoolyard. To guides and other text resources which helped them compensate for the lack of existing science materials, see that understanding behavior is central to both he and Ms. Rivera decided to combine fieldwork with the social and the biological sciences and entails some simple technology involving a computer and a grasping a set of interrelated concepts, including: scanner that Mr. Walker brought from home, as well as the school’s website. They imagined that in the • Descriptions of behavior vary in their level of beginning the simple task of cataloging the species in detail (e.g., micro to macro) and in their scope of their schoolyard would occupy much of the students’ application (e.g., behaviors of individuals, groups, time. Once fewer new species were found, students populations, and species). could begin to focus on observing the behavior of dif- • All organisms have repertoires of behavior that ferent species and changes in the density and distribu- are species specific. One can often identify reliable tion of populations. patterns in behaviors. Some behaviors are auto- From the college course Mr. Walker had taken, he matic and relatively inflexible; others are under knew that selecting biodiversity as a theme afforded voluntary control and are relatively flexible. the opportunity to develop central biological prin- ciples important to evolutionary thinking, such as: • The form and/or functions of behaviors may change over the development of an organism. • Organisms can be described as collections of Sometimes a behavior maintains its form while its attributes and can be distinguished (classified) by function changes; other times, organisms develop variation among these attributes. new behaviors to achieve a similar function. • Change in selected attributes of organisms (e.g., Mr. Walker and Ms. Rivera spent time discussing plant height) can be modeled mathematically, so the mathematical resources useful in modeling behav- that comparative study of patterns of change can ior, including representations of frequency, covaria- be conducted at the organismic level, a level with tion, distribution, function, and classification models. great initial appeal to students who grow their Mr. Walker brought in notes from his college class own plant or care for their own insect. about domain-specific models of behavior that could • The “natural histories” of organisms (e.g., life be developed with students, including rules, programs, cycles) could be described and compared. ethograms, and information-processing models. Ms. Rivera and Mr. Walker also had a large num- • Growth can be aggregated at several levels ber of students who spoke Spanish at home and a (genotypic, phenotypic, population). few students who were just learning English. Their • Population growth can also be modeled math- hope was that the project would get both English- ematically. Heritability and selection transform speaking and Spanish-speaking students excited about 23 Four Strands of Science Learning

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producing an online bilingual field guide that would be continuously updatable. Mr. Walker and Ms. Rivera began the project by arbitrarily dividing the school- yard in half. The second graders took the west side, which included the grassy front of the school, a large shade tree, a parking lot, an outside play area, and a swampy woodlot where pools formed in the spring, providing a home for frogs. The fifth graders took the east side, which abutted a street on one side and a sloping ravine that led down to a muddy, rocky stream. FIguRE 2-1 This map shows a general depiction of the Verona Area Although the two classes worked separately, they Schools Woodlot Trail, before students developed a sys- agreed to follow a common plan: first identifying tematic plan for mapping the distribution and density of trees, then shrubs, and then flowers. The two groups common species. met for an afternoon once a month to report to one another what they’d been doing and what they’d They suggested that students be organized in map- found. These monthly “biodiversity conferences” ping their sections of the yard, providing them with were popular with both classes. Mr. Walker and Ms. graph paper for a grid, but they did not insist on this Rivera took turns providing snacks for the students, (see Figure 2-1 for an example of the initial map). which they called “food for thought.” They hoped that the need for a more systematic plan In preparation for the monthly meeting, both would emerge from the students’ own questions. groups of students organized their ideas for pre- In addition to trees and plants, they identified a sentation, typically in printed handouts, posters, few different kinds of animals, including two species or pictorial form, and they worked especially hard of squirrels, one species of chipmunk, several spe- on communicating their ideas clearly. They devel- cies of birds, and many different insects. They bor- oped PowerPoint slides of what they began to call rowed a number of field guides from the local library “interim reports,” “update posters,” maps, and (Peterson’s Field Guides were the favorite), which they sometimes even drawings of the leaves or insects used to identify different plants. Shrubs were diffi- they’d found. cult to distinguish from small trees, and flowers were During the first several months, the two classes hard to identify when they weren’t flowering. These cataloged trees, shrubs, and flowers. They found became topics of intense conversation. that identifying trees was fairly easy, but the stu- As they cataloged plant and animal species, the dents, especially the second graders, had more dif- students faced several challenges. Using field guides ficulty identifying shrubs and flowers. Mr. Walker as references was sometimes confusing, as the actual and Ms. Rivera, in private conversations, grappled plants they found often looked different from the with whether they should or should not require pictures in the guidebook. Mr. Walker and Ms. Rivera the students to develop an explicit sampling plan. used this as an opportunity to steer students toward 24 Ready, Set, SCIENCE!

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the reading of expository texts. When it wasn’t clear From their initial observations, readings, and col- whether a plant was the same as the one shown lections, the students decided to map their areas more in the guidebook, students found other books or carefully. This interest in more systematic sampling materials with information on the same plant. This, grew out of a lengthy discussion in one of the month- in turn, prompted the students to find additional ly biodiversity conferences. Although both teachers information as they assembled clues: Where is the had encouraged making a grid of the yard to guide plant usually found? When does it typically bloom? their observations, the students initially did not see How tall is it? the need to map or develop a systematic plan. The Cataloging the animals in the schoolyard was students had begun with an “Energizer bunny” strat- particularly challenging. How could they tell wheth- egy: look around, write down novel species, and keep er they were seeing two different squirrels or the doing that until you don’t see any more. In compar- same squirrel twice? Long discussions ensued. Mr. ing results between the two classes—and hence com- Walker explained that what practicing biologists do paring the east and west sides of the schoolyard—the to identify particular animals is to put some kind students realized that they needed to be more system- of identifying device on them. This might entail atic in figuring out the distribution or density of com- capturing and perhaps even anesthetizing the ani- mon species. In order to do this, they shared mapping mal. They might put a colored band on a leg or techniques and some strategies for sampling to char- sometimes a spot of indelible paint (e.g., a green acterize the woodlot and ravine areas (using com- dot on the left rear foot for one squirrel and a red passes and pacing) and made explicit decisions about dot on the left rear foot for another squirrel). This, where, how, and what to sample (see Figure 2-2). of course, would not be possible in their schoolyard. With more accurate maps, they began to specu- But, he told them, not all identification requires late about the causes of variation in plant and intervention. Whale biologists, for example, rely on animal life. They wondered if a species often grew photographs of whales, identifying individuals by in one place rather than another because of the the visible pattern of whale lice on their rear flukes. other things growing around it. Careful observa- After much discussion, during which different tions that included shade, position on a slope, and proposals were considered, the students decided distance from a path where the soil is disturbed that they could do something similar to what whale took on new significance. They noticed that there biologists do. After a period of observation, they were more trees and larger trees on one side of asked if anyone had noticed squirrels with different the schoolyard than there were on the other, which characteristics—scraggly tails or bushy tails, squirrels prompted a great deal of theorizing about the with tails that are darker or lighter than their body cause: Was it sunlight, soil quality, or amount of fur, black versus brown fur, scars or bare patches, water? This, in turn, led to more systematic measure- etc. The students made drawings, took photo- ments of tree circumference and height. Mr. Walker graphs, and then attempted to record observations and Ms. Rivera realized that the students’ decision to of particular individuals or species, according to use systematic measurement had to be motivated by these characteristics. From there, the students were their own theories and investigations in order to be able to develop reasonably reliable category sys- seen as a necessary and useful technique. tems, based on which features were most diagnos- After several months, a number of the students tic in telling one squirrel from another. in each class emerged as highly skilled draftsmen 25 Four Strands of Science Learning

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This gave the tree group an opportunity to discuss variability of measures and sources of measurement error, which they shared with their classmates. Another group was primarily inter- ested in weeds, which turned out to be much harder to categorize than trees and shrubs. After weeks of debate and discussion, the group realized that the term “weed” could be used to describe any unwanted plant. The students came up with a saying that they displayed on a wall banner in both classrooms: “One FIguRE 2-2 person’s weed may be another person’s flower and This map shows a more detailed depiction of the Verona another person’s dinner.” This helped the students Area Schools Woodlot Trail, with shaded areas showing the number of different tree species in each area of the realize that how one views the world influences the schoolyard. way one describes it and to press themselves to clar- and artists, depicting the details on plant leaves, ify their assumptions and work to strive for common woody stems, and bark. The second graders created language and meaning in their scientific work. elaborate scrapbooks of pressed plants, and a group Students’ interests in the project varied widely, of four boys assembled a pinned insect collection. and not all of them were easily drawn into the In the spring, the students discovered tadpoles in course. Ms. Rivera and Mr. Walker worked hard to the pools that had formed by the marsh, and they make the children aware of different aspects of the watched, fascinated, as the tadpoles became frogs. investigation in order to help them identify their Several children who didn’t speak English own interests in the unit. Some were interested emerged as keen observers and were highly valued in such areas of study as sustainability, collecting for their artistic contributions. Others were interest- and studying insects (both alive and dead). Some ed in annotating drawings and making sure that all were interested in developing and using such tools captions and commentary were done in both English as Excel databases and other software packages to and Spanish. Ms. Rivera, who spoke both languages, aid in drawing. The students who collected and was helpful in this as well. studied the insects pursued their interest over time Gradually, interest groups emerged. One group and eventually focused on investigating insect move- was interested primarily in trees, estimating their ment. They focused primarily on the area by the age by measuring their circumference and height. In stream, as it seemed less affected by people than order to overcome the challenge of measuring the other areas of the yard and had more insects. The heights of tall trees, Mr. Walker built on the children’s students compared the locomotion of insects in understanding of the mathematics of triangles. He water with their locomotion on different ground showed them how to make a simple altimeter, which, surfaces, such as grass, mud, and pavement. along with the Pythagorean theory, the children used The students in the insect group at first wanted to to measure the heights of all of the trees in the yard. classify insects by salient attributes like color or size. 26 Ready, Set, SCIENCE!

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Mr. Walker and Ms. Rivera found it helpful to refocus trees. They had ruled out differences in soil quality, their attention on more important features like mouth but not whether the cause had to do with age or parts, by presenting “tools” analogous to mouth parts sunlight conditions or the species itself. (picks, straws, tongs, etc.) along with different kinds The following September, Ms. Rivera and Mr. of food and asking the children to investigate which Walker decided to continue their curriculum, types of food can be most easily picked up with which which they were now calling “Biodiversity in a City types of “tools.” This led to an interesting investiga- Schoolyard.” The students from the previous year tion of the “tools” that different insects had. wanted to continue their work. In response, the A number of students in the fifth grade began to third- and sixth-grade teachers asked to join the explore the history of different plantings in the yard, project with Mr. Walker and Ms. Rivera. interviewing older residents who lived nearby and The second year of the project began with pre- visiting the local history museum. After extensive sentations from the students who had developed investigation, they determined that the largest and the field guide the year before. The launching point tallest of the trees in the front yard was probably was the unfinished work and unanswered questions older than the school building itself. generated by the previous year’s second and fifth By the end of the school year, the two groups graders. The introductory session for all of the stu- had assembled an electronic field guide, with dents included these “hanging questions,” as well detailed drawings, annotated commentary in both as a number of new ones. One student wanted to English and Spanish, and a map of flora and fauna know how many trees over 60 feet tall there were in organized both by quadrants and by a much finer- the neighborhood. Another wanted to map big trees grained grid of square meters. throughout the entire city using global positioning In all, the children had identified 9 species of system technology. trees, 12 types of woody shrubs, and 14 species The two teachers were simultaneously excited of planted flowers. The field guide contained 47 about their past success and nervous about their lack detailed drawings, with separate chapters on trees, of subject matter expertise. This provided a learning shrubs, flowering plants, weeds, animals, and insects. opportunity for everyone. Mr. Walker decided to ask The two classes presented a print version of their for help from members of the biology department completed field guide to the school, to be placed on at the local college. He was amazed at the response. reserve in the library. They presented their work via Several faculty and advanced undergraduates were PowerPoint presentation at an all-school assembly. interested in visiting the school to discuss the proj- While Mr. Walker and Ms. Rivera were pleased ect. When the guest speakers came, the teachers with the results of the biodiversity project, they had as many questions as the students, asking about knew it was just the beginning. A friend of Mr. methods for pursuing the students’ questions, as Walker who worked in landscaping examined the well as soliciting factual information. field guide and pointed out several errors in clas- Despite their concerns about being able to over- sification. Moreover, despite the polished presenta- see all of these activities adequately, Mr. Walker and tion for the school and all the information they had Ms. Rivera still felt they were doing many things gathered, the students had ended up with many right. And their concern with the success of the unanswered questions. They were still unsure what project led them to reach out and find resources accounted for the variation in the heights of the they might never have otherwise. 27 Four Strands of Science Learning

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Mr. Walker and Ms. Rivera’s study of biodiversity had become a keystone for teaching science in their school. It posed questions of civic and global impor- tance. It integrated diverse modes of inquiry. It called on mathematical, histori- cal, literary, and artistic skills and tools. It provided students not only with a deep and personal relationship with their subject but also with an understanding that learning science is based on continuous and creative investigation: questioning, mapping, reflection, systematic observation, data analysis, presentation, discus- sion, modeling, theorizing, and explaining. The most exciting part was that their continued investigations inevitably led to more questions. The study of biodiver- sity offered endless opportunities for learning. Examining the Four Strands in Instruction The “Biodiversity in a City Schoolyard” case provides an example of how the four strands of science learning can be intertwined in instruction and how skills and knowledge are built over time. Strand 1: Understanding Scientific Explanations The young students in Mr. Walker’s and Ms. Rivera’s classes were not starting their study of biodiversity completely from scratch. They all came with some foundation of prior understanding, the result of personal interests and previous experience or interaction with nature. They also had a well- developed sense of the causal regularities, mechanisms, and principles of the biological world, and Mr. Walker and Ms. Rivera were able to activate and build on that knowledge. Research shows that very young children—even infants—are able to distin- guish animals (birds) from artifacts (stuffed animals), even when they have strikingly similar appearances. This may be related to their ability to distinguish intentional agents from inanimate objects, in that animals are distinctive because they are social creatures with desires, goals, and other cognitive and emotional states that help explain their actions. Young children tend not to know much about the mechanisms that underlie biological processes, such as digestion, movement, and reproduction. However, they have a remarkable ability to track various patterns in the biological world. For example, they understand that food is transformed in a manner that gives organisms the ability to grow and move and that an organism will physically 28 Ready, Set, SCIENCE!

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deteriorate if it does not eat. So they understand some of the distinctive processes that are essential to digestion. Children are also able to recognize particular aspects of or patterns related to living things: that they have an underlying nature and that they are embedded in an ordered system of groups and categories. Indeed, some aspects of children’s beliefs about biology are common across cultures, suggesting that ways of orga- nizing the living world are deeply embedded in human thinking. With opportunities such as the “Biodiversity in a City Schoolyard” course of study, children’s ideas about the living world undergo a dramatic change during elementary school. They move from seeing plants and animals as special because they possess a “vital force” to seeing them as animated by metabolic activities. They are able to explore, map, and model habitats and ecosystems. In the process, their conceptual understanding of living things undergoes significant changes: they begin to see interconnections among living things in a dynamic system. Strand 2: Generating Scientific Evidence Even though the children were young and many spoke English as a second lan- guage, much of what the students in Mr. Walker’s and Ms. Rivera’s classes were doing involved generating scientific data. They mapped the schoolyard and developed systematic ways of sampling the number and kind of plants and animals. They collected samples of plants and insects, took careful measurements, and plotted the kind and density of different plant and animal species. They drew care- ful pictures of stems, leaves, and buds and often cut them open to explore their insides. They also brought specimens inside and carried out sus- tainability studies of plants in jars, with different kinds of soil, food and sunlight. They created a laboratory to examine the life cycle of butterflies from the caterpillars they found on leaves. They recorded these changes 29 Four Strands of Science Learning

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in notebooks, Post-it notes, and wall charts and used these documents to graph changes over time. All of this documentation became “data” to think about, question, and argue with. Using these data, they could describe and discuss patterns of vegeta- tion and the relationships among vegetation and animal life. With their maps, charts, and evolving field guide, they could raise questions about the evidence they’d gathered and what it meant. If they needed more evidence, they could design investigations to answer specific questions. When their maps of the school- yard showed a different density of fall woody plants on one side, they collected more systematic evidence of the height of the trees, using handmade altimeters. They found, to their surprise, that the trees on one side of the yard were taller on average. With careful documentation of the height of the trees, the students gen- erated questions about the causes of differential tree height. Was it due to differ- ences in exposure to sunlight or water? Was it because there were different species of trees present? Or was it due to the age of the trees? These questions led to a detailed cataloging of species as well as an investigation of sunlight, ground tem- perature, and ground moisture. Good evidence led to more questions, which in turn led the students to generate more evidence. Strand 3: Reflecting on Scientific Knowledge The students in the two classes had many opportunities to reflect on their increas- ing knowledge as well as on the puzzles they encountered. In exploring the answer to the question of why the trees on one side of the yard were taller, the students were aware of the limitations of their evidence with respect to the age of the trees. When reporting on their findings after a fieldwork activity, they asked each other questions about the quality and reliability of the data they were collect- ing. Increasingly, they asked for evidence from one another when causal explana- tions were proposed. As the field guide developed over the year, there were disagreements about classifications that needed to be resolved. The students became aware of occasional mistakes and paid attention to how these mistakes were corrected, as well as to how their ideas changed over time. The most obvious example of this was the shift in students’ thinking about the differences between weeds and flowers. The field guide became a “collective memory” for the group. Updates to the guide reminded everyone of how thinking can undergo signifi- cant change. 30 Ready, Set, SCIENCE!

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Strand 4: Participating Productively in Science The scientific practices at the heart of the biodiversity work took place both out- side and inside the classroom. In addition to fieldwork in the schoolyard (map- ping, observing, drawing, plotting frequency), the students actively participated in discussions about their data, their questions, and their emerging conjectures and plans for systematically following up on these ideas. Students worked in small groups and regularly engaged in “cross-talk” sessions in which they exchanged information with other interest groups. And of course there were the monthly biodiversity conferences, moderated by Mr. Walker and Ms. Rivera. On the basis of both fieldwork and class work, the groups spent a great deal of time refining, revising, and publishing their work so that they could share it with others—other classes in the school, local experts, and members of the community. The monthly meetings of the two groups were designed to be like scien- tific conferences, and the students treated them with appropriate seriousness and respect. Attendance was nearly 100 percent on these days in both classrooms, and the students rarely misbehaved. They spent a great deal of time and effort prepar- ing their presentations. A major point of controversy that played out in the biodiversity confer- ences involved the question of what defines a “weed.” The conclusion that defining a weed was more a matter of interpretation and perspective, as opposed 31 Four Strands of Science Learning

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to scientific fact, emerged over a long period of time. Change came about as the result of disagreement, the marshaling of systematic evidence, sustained inves- tigation (which involved some surveying of students, adults, and local garden- ers), and even the help of outside experts. Early on, some students proposed surveying the school and taking a vote, while others argued that there might well be scientific evidence they could find to establish a definitive answer. This turned out to be one of the most exciting periods of investigation during the year. Issues of confidence in one’s data, the reasonableness and persuasiveness of arguments, and the fruitfulness of certain lines of investigation became the primary focus of the later biodiversity conferences. The Interrelated Nature of the Four Strands While it is possible to separate the strands for the purpose of analysis, in practice the strands overlap. A specific task might function in multiple ways and be a part of multiple strands at once. For example, in one of the monthly biodiversity conferences, a fifth-grade student, Cara, presented a chart showing plots of trees and calculations of tree heights on two different sides of the school. In showing the chart, Cara said that the tree group had determined how to measure the height of the trees using triangles and the Pythagorean theorem. But their calculations of tree height puzzled them and made them wonder if their data were accurate. A student from the audience asked if the difference might be related to sunlight because he had found in his experiment with wildflowers (growing under different conditions) that a certain wildflower grew faster and taller with more sunlight. In this brief exchange, the students were marshaling scientific explanations, using their own data as evidence, reflecting on their current understanding, and participating in authentic scientific practices as presenters and audience members. All four strands were actively in play. It is important to emphasize that the different strands inform and enhance one another. They are mutually supportive so that students’ advances in one strand tend to leverage or promote advances in other strands. In the case of “Biodiversity in a City Schoolyard,” one can see this kind of synergy growing over the course of the investigation. Prior knowledge and understanding help the students as they begin observing and recording. Their different interests lead them in different directions in the early stages of fieldwork. The collection 32 Ready, Set, SCIENCE!

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of data (Strand 2) becomes evidence that they use to reflect on and reason with (Strand 3). That, in turn, prompts them to ask more questions and search for information from a number of different sources, which leads them to a deeper understanding of the biological processes at work (Strand 1). As their under- standing of biological explanations increases, their questions and their search for evidence grow more complex and focused (Strand 2). For example, as the students come to understand the relationship between food sources and population density, they seek out better techniques for mapping popula- tions and population density in differ- ent parts of the yard. They seek out more sophisticated tools for mapping and graphing the density of certain plants and measuring the height of woody plants (Strand 2). As the sophistication of their tools increases, their evidence grows richer and their techniques more sys- tematic (Strand 2). This also leads to more disagreements about measure- ments and more discussions about the quality and reliability of data (Strand 3). Over time, the students’ reasoning about and understanding of trends and patterns grows more sophisticated (Strand 1) and their questions evolve further. They have more critical discussions about trade-offs among different methods of data collection and the fruitfulness of particular lines of investigation (Strands 3 and 4). As their questions grow more complex and their understanding of what counts as evidence grows more sophis- ticated, the design of their investigations becomes more nuanced and appropriate (Strands 1, 2, 3, and 4). The techniques that Mr. Walker and Ms. Rivera used to promote cross-talk and whole-group discussion allowed everyone to have access to the thinking, data, and discoveries of others (Strand 4). At monthly biodiversity conferences, they were able to critique one another’s proposals and designs with counterevidence and make constructive suggestions based on previous efforts (Strands 3 and 4). 33 Four Strands of Science Learning

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These investigations led to greater understanding of their schoolyard and of the ways that biologists and botanists understand the world (Strands 1 and 3). While different classroom activities will emphasize different strands at differ- ent times, the goal is to try to bring all four strands into play on a regular basis. Science as Practice: Doing and Learning Together Throughout this book, we talk about “scientific practices” and refer to the kind of teaching that integrates the four strands as “science as practice.” Why not use the term “inquiry” instead? Science as practice involves doing something and learning something in such a way that the doing and the learning cannot really be separated. Thus, “practice,” as used in this book, encompasses several of the different dictionary definitions of the term. It refers to doing something repeat- edly in order to become proficient (as in practicing the trumpet). It refers to learning something so thoroughly that it becomes second nature (as in practicing thrift). And it refers to using one’s knowledge to meet an objective (as in prac- ticing law or practicing teaching). A particularly important form of scientific practice is scientific inquiry. The term “inquiry” has come to have different meanings as the concept has been implemented in curriculum frameworks, textbooks, and individual classrooms in recent years. To reflect this diversity and to broaden the discussion of effective science teaching and learning, the Committee on Science Learning, Kindergarten Through Eighth Grade chose to emphasize scientific practices rather than the spe- cific practice of inquiry. This decision has several benefits. What we say about scientific practice applies to inquiry as well as to many other activities that take place in science classrooms. Focusing on practices also places inquiry in a broader context that can reveal when and why inquiry is effective. When students engage in scientific practice they are embedded in a social framework, they use the discourse of science, and they work with scientific repre- sentations and tools. In this way, conceptual understanding of natural systems is linked to the ability to develop or evaluate knowledge claims, carry out empiri- cal investigations, and develop explanations. This perspective is a far better characterization of what constitutes science and effective science instruction than the common tendency to teach content and process separately. When students engage in science as practice, they develop 34 Ready, Set, SCIENCE!

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knowledge and explanations of the natural world as they generate and interpret evidence. At the same time, they come to understand the nature and development of scientific knowledge while participating in science as a social process. i The diverse group of professionals who collectively build and support chil- dren’s science learning can draw from the strands in important ways. At the class- room level the individual teacher can analyze the resources at her disposal—the textbooks, trade books, science kits, and assessment instruments—and begin to consider how they support the strands. It is likely that many of these resources will provide uneven or incomplete support for some important aspects of the strands. Some teachers may be well positioned to enhance the available resources by consulting the literature or connecting with local professional development opportunities. For many others, though, it won’t be that easy. Despite her strong science background, Ms. Fredericks struggled in the classroom and ultimately found support through an informal network of colleagues who invested time and energy in helping her learn to teach science. While teacher-initiated activity like that of Ms. Fredericks and her colleagues is essential to meaningful change in K-8 science, it is not enough. School- and district-level science curriculum professionals, as well as professional development opportunities, instructional supervision, and assessment, must all play a part if meaningful change is to occur. Like the classroom teacher, educators at the school and district levels must examine the resources at their disposal, including teacher training materials, district curriculum guides, and materials adoption processes. They can examine, critique, and refine these resources to reflect the strands. They can scrutinize the professional learning opportunities available to teachers through the school system, local universities, science centers, and other vendors to identify ways to advance teachers’ understanding of the strands. The strands offer a common basis for planning, reflecting on, and improving science education. The coming chapters will show that the educator who hopes to integrate the strands into his science curriculum has a lot in common with his students. Educators, researchers, administrators, and policy makers will all have to find ways to advance their own understanding and provide support to one another as they explore and integrate this new model of what it means for children to understand and participate in science. 35 Four Strands of Science Learning

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For Further Reading Carey, S. (1985). Conceptual change in childhood. Cambridge, MA: MIT Press. Gotwals, A., and Songer, N. (2006). Measuring students’ scientific content and inquiry reasoning. In Proceedings of the 7th International Conference of the Learning Sciences (pp. 196-202). Bloomington, IN: International Society of the Learning Sciences. Lehrer, R., Schauble, L., Strom, D., and Pligge, M. (2001). Similarity of form and substance: Modeling material kind. In S. Carver and D. Klahr (Eds.), Cognition and instruction: Twenty-five years in progress. Mahwah, NJ: Lawrence Erlbaum Associates. National Research Council. (2007). Goals for science education. Chapter 2 in Committee on Science Learning, Kindergarten Through Eighth Grade, Taking science to school: Learning and teaching science in grades K-8 (pp. 26-50). R.A. Duschl, H.A. Schweingruber, and A.W. Shouse (Eds.). Center for Education, Division of Behavioral and Social Sciences and Education. Washington, DC: The National Academies Press. Stewart, J., Cartier, J.L., and Passmore, C.M. (2005). Developing understanding through model-based inquiry. In National Research Council, How students learn: History, mathematics, and science in the classroom (pp. 516-565). Committee on How People Learn, a Targeted Report for Teachers. M.S. Donovan and J.D. Bransford (Eds.). Division of Behavioral and Social Sciences and Education. Washington, DC: The National Academies Press. 36 Ready, Set, SCIENCE!

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3 Foundational Knowledge and Conceptual Change Recent research has revolutionized views of how children’s minds develop from infancy through adolescence. The past 20 to 30 years of research have shown that children come to school with a great capacity for learning in general and learning science in particu- lar. Even preschool children have a rich set of ideas, conceptual frameworks, and reasoning skills. They bring to school rudimentary “theories,”1 rules of thumb, and general principles that help them separate the world into different domains and organize their expectations about how things ought to behave. Their under- standing of the world helps them explain phenomena and solve problems. They are able to engage in surprisingly sophisticated scientific thinking in the early grades and can appreciate deep points about the nature of science. This is good news for educators committed to improving science learning for students. It also raises a number of questions that are explored throughout this book: • How does one recognize the knowledge that children bring to school? • How does one build on this knowledge in ways that specifically support science learning? • How does one make diversity (in culture, language, or prior experience) a resource rather than an obstacle? • How does one integrate the four strands of science learning so that each informs and enhances the others? Elements of all four strands of science learning can be seen in the capabili- ties and knowledge that children bring with them to school. This means that the four-strand framework described in Chapter 2 can and should begin as soon as 37